Impulse-forming and like machines



p 9'70 F. E. BENNETT HAL 3,526,121

IMPULSE-FORMING AND LIKE MACHINES Filed Dec. 12, 1967 5 Sheets-Sheet 1 Sept. 1, 197% B N TT ETAL 3,526,121

IMPULSE-FORMING AND LIKE MACHINES Filed Dec. 12, 1967 5 Sheets-Sheet 2 Sept-'1', 1978' F. E. BENNETT 'Er AL 3,526,121"

IMPULSE-FORMING AND LIKE MACHINES 5 Sheets-Sheet 4 Filed Dec. 12, 1967 k SQ BSU Sept. 1, 1 'l F. E. BENNETT ET AL IMPULSE-FORMING AND LIKE MACHINES Filed Dec. 12, 1967 5 Sheets-Sheet 6 FIG.6.

United States Patent US. Cl. 72453 9 Claims ABSTRACT OF THE DISCLOSURE In an impulse-forming, forging or like machine of the kind in which the moving member is moved by pressure of a gas, possibly air, applied initially to a sealed portion of the operating area of a piston member, the seal being broken subsequently to enable the pressurized gas to be applied suddenly to substantially the full operating area of the piston to cause said moving member to be impulsed, means are provided substantially to prevent impulsing when there is likelihood of the impulsive force delivered by the machine being below a predetermined level. Thus stops may be provided for preventing impul sive movement of the moving member, said stops being adapted to be withdrawn only when the machine is in fully operational condition. Delays are introduced especially during warm-up periods and also if the fuel supply line to a combustion energised system is not correctly pressurized.

This invention relates to impulse-forming machines of the kind described in Pat. No. 3,253,399. In machines of this kind, energy derived from release of chemical energy of a material, for example by combustion, is caused to be applied to a piston operating in a cylinder and in turn,'to a device for acting on a workpiece. In this way, the high energy of the fast-moving piston can be fed into the workpiece to perform a particular forming or like operation, such as shaping, deforming, cropping, blanking, etc.

The operation of the machine described in the aforesaid pending application depends upon a seal between the piston and an opening from the reaction chamber being maintained by back pressure caused by compressed gas, such as compressed air, until the energy released by the chemical reaction is built up to a certain extent, the area of the piston exposed to the increasing pressure being smaller than the cross-sectional area of the piston cylinder. When the pressure has increased to the extent that the back pressure is overcome, the seal is broken and the reaction pressure is applied to the whole of the pitson area, with the result that the piston accelerates to provide the necessary impulse to the operative device.

It has been found that, in some circumstances, the seal is broken, and the rapid expansion of the combusting gases commenced, before combustion has progressed to the extent that a suitable pressure has built up in the reaction chamber; the result is that not only is the combustion efiiciency somewhat lower than desirable but the machine may be impulsed prematurely and less effectively.

In this respect, if automatic vent valves fail to operate in correct sequence, there may be difficulty in ensuring that the seal is thoroughly seated under back pressure, by reason of the retention of high pressure gases in the space between the piston and the top of the cylinder, this having the possible consequence of premature, and inefficient, movement of the piston when the engine is fired.

Also, there is the probability of ineflicient operation of 3,526,121 Patented Sept. 1, 1970 the machine during the process of starting up from cold. After the machine has been allowed to cool down, the energy level of the impulsive force that could be imparted to the piston would not be under control during an unspecified number of cycles until the system has warmed up to substantially optimum conditions.

It is an object of the present invention to provide means of removing such disadvantages, or some of them, or at least reducing their effects.

In accordance with one aspect of the invention means are provided automatically to prevent impulsing where there is likelihood of the impulsive force delivered by the machine being below a predetermined level.

In accordance with another aspect of the invention there is included in the machine means for engaging the impulsed part of the machine so as to prevent impulsing thereof, said means being arranged automatically to be positioned for engagement of the impulsed part substantially in the cooked position of the latter and being adapted to be released only upon the machine being in a state of operative readiness.

In accordance with a further aspect of the invention, means are provided for prevention of impulsing of the operating piston upon the commencement of firing when the machine is cool, at least until the machine has warmed up sufiiciently. Such means are preferably stops, such as wedges, automatically inserted against the piston, or associated moving part, at least when the machine is cool; these means may be arranged to be electrically operated, such as by sequence switching.

The invention will now be described with reference to the accompanying drawings which illustrate, by way of example, embodiments of the invention in its different aspects.

FIG. 1 illustrates the application of the invention to an impulse-operating machine in which a part is impulsed downwardly and shows in a very general outline a side view of the machine with locking members in place for preventing movement of the impulse part of the machine;

FIG. 2 shows in section a detail of one of the locking members referred to in relation to FIG. 1;

FIG. 3 is a logic diagram illustrating one means of ensuring control of operation of the locking members only when the impulse generating means is in full functional order;

FIG. 4 shows a practical way of putting the logic of FIG. 3 into practice;

FIGS. 5 and 6 are sections of a form of seal member for attachment to the piston member of the impulse generating means for impulsing the moving part of the impulse-operating machine of FIG. 1.

It is to be understood that the scope of the invention is not to be confined to the particular embodiments illustrated and that these are included only as examples of putting the invention into effect.

In FIG. 1 of the accompanying drawings, an arrangement of impulse-forming device in accordance with Pat. No. 3,253,399 is shown in which the platen 7 of the machine is held by the stops 8, 8' in a position such that the piston is held in the position maintaining the above mentioned seal around the opening to the reaction chamber. These stops may be electrically, pneumatically, or hydraulically-operated and FIG. 2 illustrates an example of pneumatic unit. In FIG. 2, the stop member 8 has a platenengaging portion 10 on the end of a stem-shaft 11 which is formed with a piston portion 12. The piston 11 operates within a cylinder formed by the inner wall of casing 13 which provides a bearing for the portion 10 and which is sealed by an end cap 14 in which the stem-shaft 11 slides. A spring 15 urges the piston portion 12 towards an end of its stroke, as illustrated, the space at the end of the cylinder communication through the bore 16 with a pressure-hose connection 17. A borehole 18 in the end cap 14 provides a connection between the space at the side of the piston and a hose connection 19.

Normally, the stop portion 10 will be in the position illustrated, and when it is required to withdraw them, pressurized fluid is introduced in each case through the bore 16 to the end face of the piston member 12 to force the piston against action of the spring 15 to withdraw the stop portion. Subsequent release of the pressurized fluid through the bore 16 will cause the stop member to be moved into the extended position once more.

Other forms of stop will be evident to those skilled in the art and need not be elaborated here. It will be clear that such stops may be used as a safety device to hold the impulsing part of the machine against accidental opera tion when the machine is being serviced or parts are being changed.

It will also be evident that such stop devices may be used to ensure that the impulse machine is restrained from operation before a certain period has elapsed, or until certain conditions, such as temperature stability, have been achieved in the system.

In accordance with yet a further aspect of the invention means are provided for ensuring that the reaction chamber is in acceptable heat condition and preferably also that the fuel supply lines are acceptably pressurized.

Reference should be made to FIG. 3 of the accompanying drawings in order that this aspect of the invention may be better understood. This figure is a logic diagram for part of the control system of an impulse forging machine and illustrates the controls necessary to ensure that the machine may be automatically brought up to working conditions before forging.

For eflicient running, two requirements must be met and these are:

(i) that the cylinder head temperature is up to some established running level,

(ii) that an appropriate pressure exists in the fuel-injection lines.

These two parameters are continuously monitored and signals are fed to switches S2 and S4. Only that part of the controls is indicated which is concerned iwth an actual forging operation by the machine.

Switch S1 is a selector switch set by hand when a forging operation is required to be carried out; the condition of the control circuit is then automatically set by the combined states of switches S2 and S4 which act through AND gate A6 and OR gate 01. If both cylinder head temperature (S2) and fuel injector pressure (S4) are at or above their running levels (logical 1) then AND gate A1 is enabled through the action of AND gate A6. Actuation of pushbutton PBl will then start normal run ning. However, if either of S2 and S4 is below its running level then AND gate A1 is not enabled and actuation of pushbutton FBI has no effect. However, AND gate A2 is enabled and pushbutton PB2 can start the warm-up mode (which is mutually exclusive with normal running).

Two actions are taken for warm-up:

(i) the platen locks are operated and the platen is locked in the up position,

(ii) a delay (D2), say, of seconds, is introduced into the timing cycle for the exhaust valve operation, so as to hold the hot-combusted gases in the combustion chamber for that extra period.

The platen locks operate by a fail-safe circuit and so are applied by de-energizing line L3; the delay (D2) in the cycle is introduced into the open exhaust valve instruction line using AND gate A4.

Warm-up must be started manually by a pushbutton PB2; this is intended to provide an additional safeguard against unintentional firing. Once begun, cycling is continuous wnile pushbutton PB2 is operated and until both S2 and S4 have changed to the hot and pr e ccn i tions respectively. This repetitive running is distinct from -multistate of normal running and the control circuit is arranged to provide for warming up only if single is selected on S3. If this provision were not made the machine could pass directly into a normal forging and th1s change-over would be most hazardous.

Both S2 and S4 can change state at any point during a firing cycle, and the circuit is arranged to allow for the completion of that particular cycle. A delay D3) of, say, 2 seconds, is introduced into line L3 to ensure that the platen locks do not open before this last cycle iscornplete. Normal firing is not possible, therefore, unt1l this delay period has elapsed after completion of warm-up.

The logical functioning of the circuit has been realised using electromechanical elements and a specific circuit configuration is contained in FIG. 4 of the accompanying drawings.

The operation of these circuits will be evident to those skilled in the art. On switching the selector switch to forge, power is supplied to the control circuit.

Assuming that the machine is cold (indicated by the machine cold lamp), the forge/warm-up relay will be in a de-energized state. The delay relay is also in the deenergized state when the machine is cold thereby keep ng the platen latches at rest and ensuring that the machlne ram is locked. In the de-energized state the delay relay contacts are arranged to supply power to the machine cold lamp and to the synchronous motor circuit (timer motor) of a process timer unit which is used as an adjustable delay timer for the warm-up recycling of the machine. The contacts on the forge/warm-up button and recycle relay are in circuit, and the exhaust valve open instruction from the cam timer is routed via the process time delay.

On depressing the warm-up button power is supplled via the single/multi/warm-up switch (which must be in the warm-up position), and the forge/warm-up relay to the motor of the cam timer unit and thus commences the firing sequence. The first operation of the unit is to close the switch S1 thereby ensuring that the unit continues to operate for one revolution of the cams after release of the button. The cams revolve producing the prearranged valve timing sequence finally coming to rest when S1 is open as the last operation.

Towards the end of the sequence, a pulse is generated by switch S2 and this is arranged to operate the electromagnetic clutch (timer clutch) of the process timer delay thereby initiating the time delay. After the delay period which can be varied up to a maximum of 20 seconds, a signal from the process timer opens the exhaust valve and pulses recycle relay. The recycle relay closes long enough for it to short out the warm-up button and set the cam timer motor in motion again. The cycle of operation is therefore repeated. The recycling continues until a predetermined temperature is reached (pre-set on the temperature control unit). At this point a signal from the temperature control unit energizes the forge/warm-up relay.

The operation of this relay breaks the recycling loop preventing any re-firing taking place in the warm-up mode and connects the exhaust valve open line to its normal operating conditions. At this point control is also switched from the warm-up button to the forge button.

The delay relay is also energized by the temperature control unit but due to the delay in time (greater than one firing cycle) it fails to operate until the cam timer is stopped on the final cycle of the warm-up operation. After the delay period has elapsed, the delay relay switches off the process timer motor and the machine cold lamp then operates the platen latches unlocking the machine ram ready for forging.

To operate the machine it is now necessary to turn the single/multi/warm-up switch ot the single position and depress the forge button. The supply is now routed via the single/multi/warm-up switch through the safety circuit (a switch incorporated in the machines guards and cabinet panels) and the fOrge/warm-up relay to the cam timer motor, thus commencing the firing cycle of the machine. The cam sequence is virtually the same as the warm-up mode except that the exhaust open signal is taken direct from the cam timer switch and the process timer clutch pulse is suppressed. The supply for the machine set lamp is taken from the same source as the forge/ warm-up relay.

The fuel pressure switch is incorporated in the circuit to ensure that the machine cannot be used in the forge mode unless the line has been primed.'

In accordance with another feature of the invention, means are provided for controlling the rate of increase of total thrust on the piston due to reaction pressure, as the said seal is broken. Such means may comprise obturating means associated with the opening from the reaction chamber, the obturating means being adapted to cause throttling of the expansion of the reaction gases into the cylinder. By delaying application of full pressure from the expanding gases on the full area of the piston, it may be arranged that the combustion is proceeded to an advanced stage before the true impulse stroke is commenced and the combustion efliciency may therefore be enhanced, thus overcoming one of the disadvantages mentioned above. The obturating means may comprise a sleeve portion on the piston, arranged to project into the said opening to the reaction chamber, the sleeve portion being arranged to co-operate with the wall of the opening to provide a construction for gases expanding from the reaction chamber; the sleeve portion may be shaped to provide a decreasing construction and may have one or more apertures through which reaction gases may pass to the cylinder as the aperture(s) become(s) free of the obstructing wall of the opening. The sleeve portion will be of such length as to provide the desired restriction of flow during at least the initial travel of the piston.

One embodiment of this feature is illustrated in FIGS. 5 and 6 of the accompanying drawings, which show, respectively, a plan view and a view on the line XX in FIG. 5 of a seal member arranged for attachment to the piston member of an impulse-forming or like machine.

In these drawings, the seal member is formed with a main portion 1 and a flange portion 2, the portion 2 being formed with a bore 3 whose wall is parallel to the axis of the piston member to which it is attached in operation and an outer surface that is tapered inwardly away from the main portion. The flange portion 2 is formed with eight equally spaced circular holes 4 though these may be of other shape and possibly may be slotted. At its face, the portion 2 is formed with a sealing surface 5 arranged to provide the required seal against the seating 6 in the cylinder head around the opening to the reaction chamber of which the outlines are shown in FIG. 6.

It will be seen that, in the pre-firing position, the piston forces the sealing surface 5 against the co-operating seating 6 on the cylinder head, a backing pressure of compressed air being applied to the piston to maintain this seal. Upon the pressure in the reaction chamber rising, as a result of energy developed from the reaction after firing, the pressure on the piston over the surface represented by the area Within the confines of seating 6 will be increased, until this pressure overcomes the backing pressure due to the compressed air. Then the seal will be broken and the gases in the reaction chamber will expand into the cylinder over the full area of the piston member (not shown). However, at first, the expansion of the gases is impeded by the constriction presented by the flange portion 2; but very soon after the seal is broken, the holes 4 are exposed to the cylinder space and the flow area for the expanding gases is increased. When the flange portion 2 moves clear of the opening the full flow rate of the gases is achieved and the piston member accelerates to provide the necessary impulse to the device for performing or forming or like operation.

In accordance with yet another feature of the invention, the space between the piston member and the cylinder head is arranged to be permanently vented through a restricted vent 25, which may be provided by a needle valve and in consequence be adjustable. By this means, it is possible to eliminate any danger of residual pressure remaining in the space to the extent that the seal at the seating 6 is not maintained prior to a firing. Such remain ing residual pressure is more likely to arise if the space is arranged to be vented automatically by a normally closed valve which requires to be operated in correct sequence; the valve might malfunction due to sticking or it may possibly be closed too early in the sequence.

We claim:

1. In an impulse-forming machine comprising a piston and which operates by the build-up of impulsive energy behind the piston, a locking arrangement comprising:

catch means; and

control means responsive to operating conditions in the impulse-forming machine to permit the catch means to prevent impulsive movement of said piston whenever the operating conditions of the machine are such as to indicate a substantial likelihood of any impulse force delivered by the machine being below a predetermined value.

2. An impulse-forming machine as in claim 1 in which the piston is associated with an energy chamber for internal combustion of a fluid fuel, and said locking arrangement control means includes heat sensitive detecting means adapted to sense when parts of the machine associated with internal combustion are sufficiently hot for impulsing to commence.

3. An impulse-forming machine as in claim 1 in which the piston is associated with an energy chamber for internal combustion of a fluid fuel, and said locking arrangement catch means includes pressure sensitive means and a fuel supply line to said energy chamber associated with said pressure sensitive means, wherein said catch means is operatively adapted to sense if the pressure in the fuel supply line falls below some predetermined value.

4. An impulse-forming machine as claimed in claim 1 including electric circuitry adapted to operate in accordance with sequence switching methods and wherein said control means is operatively associated with said circuitry.

5. An impulse-forming machine as in claim 1 includmg:

a cylinder for said piston;

an energy chamber associated with said cylinder wherein an opening is defined from said energy chamber into said cylinder;

obturating means operatively associated with said piston to discourage movement of the piston until said impulse energy acquires a value sufiicient to give an impulse force of said predetermined value; and wherein the catch means prevents impulsive movement of the piston until the impulsive energy behind the piston reaches said predetermined magnitude.

6. An impulse-forming machine as claimed in claim 5 wherein the obturating means comprises a contoured portion projecting from the piston, surfaces to said energy chamber defining a hole for receiving the said contoured portion and outer surfaces to said contoured portion together providing a constriction for gases expand ing from the energy chamber into said cylinder for impulsing the piston.

7. An impulse-forming machine as claimed in claim 6 wherein said contoured portion is a hollow sleeve apertured in its wall portion and presenting an opening to the energy chamber, surfaces of the opening from the energy chamber to the cylinder being adapted effectively to close the apertures in said wall portion of the sleeve when the sleeve is seated in said hole defined by the energy chatrnber surfaces.

8. An impulse-forming machine as claimed in claim 1 comprising a cylinder for the piston and a restricted vent 7 for permanently connecting to atmosphere the space between the piston and the cylinder head.

9. An impulse-forming machine as claimed in claim 8 wherein the restricted vent includes an adjustable needle valve.

References Cited UNITED STATES PATENTS Bollar 72-453 Muller 72--453 Bakhtar 72453 Reischer 72-453 Hugi 72-453 CHARLES W. LANHAM, Primary Examiner G. P. CROSBY, Assistant Examiner 

